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P1a Energy & Energy Resources Mr D Powell. Mr Powell 2008 Index Heat Transfer p226-241 1 1.

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Presentation on theme: "P1a Energy & Energy Resources Mr D Powell. Mr Powell 2008 Index Heat Transfer p226-241 1 1."— Presentation transcript:

1 P1a Energy & Energy Resources Mr D Powell

2 Mr Powell 2008 Index Heat Transfer p226-241 1 1

3 Mr Powell 2008 Index 1.1 Thermal Radiation p228 Thermal (infra-red) radiation is the transfer of energy by electromagnetic waves. All bodies emit and absorb thermal radiation. The hotter a body is the more energy it radiates. Thermal (infra-red) radiation is the transfer of energy by electromagnetic waves. All bodies emit and absorb thermal radiation. The hotter a body is the more energy it radiates.

4 Mr Powell 2008 Index Thermal Radiation Quick Questions 1 Where does this planet get its energy from? 2What does a prism do to white light? 3 What is the rough temperature of the surface of the sun? 4What does thermal mean? 5What is infra red radiation? 6 Why is infra red radiation captured by the atmosphere and not UV or visible 7 How can we reduce the greenhouse effect? 8How can you tell if a metal is very hot 9Do all objects give out thermal radiation 10Do all objects absorb thermal radiation

5 Mr Powell 2008 Index Thermal Radiation Quick Questions 1Where does this planet get its energy from? Sun 2What does a prism to do white light? disperse it 3 What is the rough temperature of the surface of the sun? 5500 C 4What does thermal mean? heat 5What is infra red radiation? thermal radiation beyond visible red light 6 Why is infra red radiation captured by the atmosphere and not UV or visible (A*-C) it has a longer wavelength 7How can we reduce the greenhouse effect? reduce emissions of certain gasses like methane, CO 2 8How can you tell if a metal is very hot glows brightly 9Do all objects give out thermal radiation yes 10Do all objects absorb thermal radiation yes

6 Mr Powell 2008 Index Seeing at Night 1.Can you identify the objects? 2.Now write down a list and explain which parts are hot parts compared to the cold parts? 3.Why might this be?

7 Mr Powell 2008 Index Energy Movement 1.Watch the FLV of the snapshots shown. 2.For each one explain what you are seeing in terms of energy transfers. Pouring water Breast Exams Thermometers

8 Mr Powell 2008 Index Temperature & Colour Theory.... The main frequency (or colour) of emitted radiation increases as the temperature increases. For example, a red hot object radiates most in the long wavelengths of the visible band, which is why it appears red. If it heats up further, the main frequency shifts to the middle of the visible band, and the spread of frequencies mentioned in the first point make it appear white. We then say the object is white hot..

9 Mr Powell 2008 Index Order of Temperature In a team sequence these images into an order for which is hottest and which is coolest. Try and work out what the clues were Sparkler Light bulb Ice water Sun Sunny day Fire

10 Mr Powell 2008 Index Order of Temperature Ice water 0 Sunny day 23 Light bulb 247 Fire 500 Sun 5500 Sparkler 1000-1600 Make sure your write out the list and put a reason to explain why you put them in this order.....

11 Mr Powell 2008 Index Homework... Infra-red satellite imagery is used in weather forecasting and analysis of land use. Investigate how IR satellites are used to monitor the weather and to analyse how land is used in different countries. Find out how different types of vegetation or habitation show up in infra- red imagery or even other parts of the electromagnetic spectrum. There are many excellent images available to explore on the Internet; you could start with the various land sat or weather forecasting web sites. Write up: Produce a paragraph of your findings with any diagrams or pictures you can print off.

12 Mr Powell 2008 Index 1.2 Surfaces & Radiation p230 Dark, matt surfaces are good absorbers and good emitters of radiation. Light, shiny surfaces are poor absorbers and poor emitters of radiation. Dark, matt surfaces are good absorbers and good emitters of radiation. Light, shiny surfaces are poor absorbers and poor emitters of radiation.

13 Mr Powell 2008 Index Groups? 1.In a team group these images to reflect their energy characteristics. 2.Elect a spokesperson to explain why you have done this!

14 Mr Powell 2008 Index Theory of EM Radiation EM radiation is produced by objects all the time even though they dont appear to be doing much. It is in fact internal energy from the object converted to either visible EM radiation i.e. ROY-G-BIV or non visible light Infra red. It is the infra red part that makes them feel hot!

15 Mr Powell 2008 Index Absorption & Emission of EM Radiation 1.A perfect black object absorbs all the visible light and IR then emits the IR really well. It feels hotter to the touch 2.A perfect white object reflects all the colours and IR and UV radiation. It feels cooler to the touch. 3.A good example is white lines on our roads...or a t-shirt 4.Look at the demo of shiny v matt for visible light as an example!

16 Mr Powell 2008 Index Shiny or Dull Theory... 1.A mirrored surface reflects all the radiation striking it and absorbs none. Therefore a mirror cannot emit large amounts of radiation. 2.A matt dull surface absorbs more radiation due to cavities in the surface. (crevices) 3.A polished ring will be cooler than a dull one. Extension TASK – Now answer the questions on page 213

17 Mr Powell 2008 Index Solar Panels Now you have listened to your teacher explain how a solar panel works make up your own flowchart to explain the process (including diagrams). Fill in as much detail as you can and use as many steps you as want! Extension Task Now imagine you science consultant who designed the panels got his science the wrong way around. What mistakes could he have made to make the panel useless!

18 Mr Powell 2008 Index Leslie Cube... You an investigate the whole process by using a Leslie Cube...

19 Mr Powell 2008 Index Reflectors & Absorbers... 5 mins later 5 mins later Dark matt surfaces emit (give out) more radiation…than light shiny surfaces at the same temperature.

20 Mr Powell 2008 Index Reflectors & Absorbers... Dark matt surfaces are better absorbers (poorer reflectors) of radiation…than light shiny surfaces at the same temperatures. 5 mins later 5 mins later

21 Mr Powell 2008 Index The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation. Emission experiment... Four containers were filled with warm water. Which container would have the warmest water after ten minutes? Shiny metal Dull metal Dull black Shiny black shiny metal radiation dull black emitting

22 Mr Powell 2008 Index Absorption experiment... Four containers were filled with warm water. Which container would have the warmest water after ten minutes? Shiny metal Dull metal Dull black Shiny black The __________ container would be the warmest after ten minutes because its surface absorbs heat _________ the best. The __________ container would be the coolest because it is the poorest at __________ heat radiation. dull black radiation shiny metal absorbing

23 Mr Powell 2008 Index Decisions See if you can you sort these in the correct order of which would be the best absorbers of heat.... Shiny Black Car Shiny Steel Car Dull Black Car Brushed Steel Car Dull Black Car Shiny Black Car Brushed Steel Car Shiny Steel Car

24 Mr Powell 2008 Index 1.3 Conduction p232 The transfer of energy by conduction... involves particles and how this transfer takes place. The bigger the temperature difference between a body and its surroundings, the faster the rate at which heat is transferred. The transfer of energy by conduction... involves particles and how this transfer takes place. The bigger the temperature difference between a body and its surroundings, the faster the rate at which heat is transferred.

25 Mr Powell 2008 Index Atomic Structure Everything is made up of molecules. Molecules are not the same. Plastic is made of thousands of atoms. Glass is made of just three. Metals are never made of molecules but always single atoms. This is why they behave differently They all have unique properties Glass Molecule Plastic Molecules Metal atoms 7 mins

26 Mr Powell 2008 Index What are electrons… 7 mins Smallest thing you can think of is an Atom. But we can go deeper than that. But most of it is space! Most of the mass is the nucleus in the middle. Tiny electrons orbit the nucleus and that forms the atom They almost form a shell around it as they travel so fast (tennis balls and boy) Electrons are held by forces inside the atom The nucleus is very tiny A whole atom is a lot bigger than the nucleus 7 mins

27 Mr Powell 2008 Index Conduction 7 mins Stir a boiling liquid with a plastic ladle after a while it will become warm. So will a wooden ladle. However, a metal ladle will quickly burn your hands. All these materials conduct heat at different rates Molecules or Atoms bumping at speed into their neighbours transmit the energy. It is like a row of dominos Free electrons can travel to move extra energy They give the atoms extra vibrational energy. This makes all metals a good conductor because of their structure 7 mins

28 Mr Powell 2008 Index What is Conduction.. 7 mins On your printed sheet try and examine the information you have been given both visually, orally and in written form. Answer the three questions on the sheet. There is space for a diagram as well. Continue onto the back of your sheet if you feel the need to. 1.What happens? 2.Why does it happen? 3.How does it happen? 1 1 2 2 3 3 A good answer will have to include; o Ideas of atoms / molecules o Structure of atoms & electrons o Movement of electrons/ energy o Ideas of vibrational energy 10 mins

29 Mr Powell 2008 Index Heat Transfer in a Solid by Conduction... Heat energy can move through a substance by conduction. Metals are good conductors of heat, but non-metals and gases are usually poor conductors of heat. Heat energy is conducted from the hot end of an object to the cold end. The electrons in piece of metal can leave their atoms and move about in the metal as free electrons. The parts of the metal atoms left behind are now charged metal ions. The ions are packed closely together and they vibrate continually. The hotter the metal, the more kinetic energy these vibrations have. This kinetic energy is transferred from hot parts of the metal to cooler parts by the free electrons. These move through the structure of the metal, colliding with ions as they go.

30 Mr Powell 2008 Index Quick Fire Questions 1.Wood is a fossil fuel. 2.Oil is formed from dead plants being crushed under huge pressure. 3.Heat transfers through plastics more easily as they have lots of free electrons. 4.Carpet is a poor conductor as it has no free electrons. 5.Energy travels through roof tiles by conduction. 6.Metals are good conductors as they have lots of free electrons. 7.Energy does not travel by conduction through space. 8.A wooden spoon is a good conductor of heat and electricity 9.Metals have a structure like a single molecule 10.Glass has a structure made of three atoms which makes it a poor conductor 5-8 mins A* = 10 A = 9 B = 8 C = 7 D = 6 E = 4-5

31 Mr Powell 2008 Index 1.4 Convection p234 The transfer of energy by convection involves particles and how this transfer takes place. Under similar conditions different materials transfer heat at different rates. The transfer of energy by convection involves particles and how this transfer takes place. Under similar conditions different materials transfer heat at different rates.

32 Mr Powell 2008 Index C, C& R Quick Questions 1 Metals transfer heat by..... 2 Liquids and gases transfer heat mainly by..... 3 Light is the transfer of energy by....... 4 Free electrons moving through a substance indicate that it is a.... 5 What place would you tap water off a hot water tank & why... 6 The sea breeze in the daytime is towards the.. 7 Why does a vacuum flask keep you tea hot? 8 Why are radiators painted white instead of dull black? 9 What effect does cavity wall insulation stop completely. 10 Loft Insulation works by....

33 Mr Powell 2008 Index C, C& R Quick Questions 1 Metals transfer heat by.....Conduction 2 Liquids and gases transfer heat mainly by.....Convection 3 Light is the transfer of energy by.......Radiation 4 Free electrons moving through a substance indicate that it is a.... Conductor with metallic structure 5 What place would you tap water off a hot water tank & why... At the top as hot water rises (Convection) 6 The sea breeze in the daytime is towards the.. 7 Why does a vacuum flask keep you tea hot? 8 Why are radiators painted white instead of dull black? 9 What effect does cavity wall insulation stop completely. 10 Loft Insulation works by....

34 Mr Powell 2008 Index C, C& R Quick Questions 1 Metals transfer heat by.....Conduction 2 Liquids and gases transfer heat mainly by.....Convection 3 Light is the transfer of energy by.......Radiation 4 Free electrons moving through a substance indicate that it is a.... Conductor with metallic structure 5 What place would you tap water off a hot water tank & why... At the top as hot water rises (Convection) 6 The sea breeze in the daytime is towards the.. Land as it heats up more quickly than the water (Convection) 7 Why does a vacuum flask keep you tea hot? The energy cannot conduct through a vacuum 8 Why are radiators painted white instead of dull black? So that the heat is not all conducted out of the first radiator in the system! 9 What effect does cavity wall insulation stop completely. Convection Currents in the cavity 10 Loft Insulation works by.... Trapping hot air in the fibres to reduce conduction and convection

35 Mr Powell 2008 Index What is convection This is the way heat is transferred in liquids and gases. It depends on, in general, fluids expand when heated and become less dense. This is a domestic hot water tank.

36 Mr Powell 2008 Index Convection Currents A current, called a convection current becomes present in the liquid If heat is supplied. Cooler liquid falls. Warmer, less dense liquid rises. The cycle continues as the heat is supplied

37 Mr Powell 2008 Index The Earths Crust... The Earths lithosphere (the crust) is cracked into a number of large pieces (tectonic plates) which are constantly moving. This is as a result of convection currents within the Earths mantle driven by heat released by natural radioactive processes.

38 Mr Powell 2008 Index Radiators The heat from a radiator causes the warm air to rise and as the air rises then it cools and becomes denser. The cool air falls and replaces the warm air which is rising. And the cycle continues until the radiator cools.

39 Mr Powell 2008 Index Thermometers.... Can you explain what is happening here in terms of particle behaviour in as much detail as possible. Write your own paragraph and diagrams to help you. You might want to start like this... We can see that...... This is because....... Firstly the..... Secondly the..... Thirdly the..... In conclusion...... Key Words: Particles, Temperature, Kinetic Energy, Thermal, Heat, Expansion

40 Mr Powell 2008 Index Convection Currents Modelled by Peas.... Can you explain what is happening here in terms of particle behaviour in as much detail as possible. Write your own paragraph and diagrams to help you. You might want to start like this... We can see that...... This is because....... Firstly the..... Secondly the..... Thirdly the..... In conclusion...... Key Words: Particles, Temperature, Kinetic Energy, Thermal, Heat, Expansion, rises, falls

41 Mr Powell 2008 Index Creative Writing Firstly watch the FLV movie on Convection. As you are watching the movie make some short hand notes to remind you of what you have seen. Now use this and the items you have covered in the lesson to write a structured set of paragraphs and diagrams which comprehensively explains the term Energy Transfer by Convection You can also use anything else you can thing of to add to this!

42 Mr Powell 2008 Index Question 1 Although we have not talked about all types of energy transfer can you fill in some of the blanks for this question. Try and reason out the missing ones? electrons ions collisions waves

43 Mr Powell 2008 Index Question 2

44 Mr Powell 2008 Index Question 3 matt surfaces shiny surfaces Infra red particles

45 Mr Powell 2008 Index Thermal Radiation Quick Questions 1 2 3 4 5 6 7 8 9 10


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